<?php
// $Id: nodeapi_example.module,v 1.1.2.4 2010-12-28 20:46:28 rfay Exp $

/**
 * @file
 * This is an example outlining how a module can be used to extend existing
 * content types.
 *
 * We will add the ability for each node to have a "rating," which will be a
 * number from one to five.
 */

/**
 * @defgroup nodeapi_example Example: NodeAPI
 * @ingroup examples
 * @{
 * Modifying a node during its life-cycle. (drupal 6)
 *
 * This example demostrates 'piggy-backing' some data on the
 * node in another database table.
 *
 * This example is part of the Examples for Developers Project which you can download
 * and experiment with here: http://drupal.org/project/examples
 */

/**
 * Implementation of hook_form_alter().
 *
 * By implementing this hook, we're able to modify any form. We'll only make
 * changes to two types: a node's content type configuration and edit forms.
 *
 * We need to have a way for administrators to indicate which content types
 * should have our rating field added. This is done by inserting a checkbox in
 * the node's content type configuration page, in the 'Workflow' group.
 */
function nodeapi_example_form_alter(&$form, $form_state, $form_id) {
  if ($form_id == 'node_type_form' && isset($form['identity']['type'])) {
    // Alter the node type's configuration form to add our setting. We don't
    // need to worry about saving this value back to the variable, the form
    // we're altering will do it for us.
    $form['workflow']['nodeapi_example'] = array(
      '#type' => 'radios',
      '#title' => t('NodeAPI Example Rating'),
      '#default_value' => variable_get('nodeapi_example_'. $form['#node_type']->type, 0),
      '#options' => array(0 => t('Disabled'), 1 => t('Enabled')),
      '#description' => t('Should this node have a rating attached to it?'),
    );
  }
  // If the type and node field are set this may be a node edit form.
  elseif (isset($form['type']) && isset($form['#node']) && $form['type']['#value'] .'_node_form' == $form_id) {
    // If the rating is enabled for this node type, we insert our control
    // into the form.
    $node = $form['#node'];
    if (variable_get('nodeapi_example_'. $form['type']['#value'], 0)) {
    // Note that $form['nodeapi_example_rating'] will become
    // $node->nodeapi_example_rating in hook_nodeapi validate op
    // This also means that if there is a fieldgroup defined,
    // $form['group']['field'], that it will become $node->field.
      $form['nodeapi_example_rating'] = array(
        '#type' => 'select',
        '#title' => t('Rating'),
        '#default_value' => isset($node->nodeapi_example_rating) ? $node->nodeapi_example_rating : '',
        '#options' => array(0 => t('Unrated'), 1, 2, 3, 4, 5),
        '#required' => TRUE,
        '#weight' => 0,
      );
    }
  }
}

/**
 * Implementation of hook_nodeapi().
 *
 * We will implement several node API operations here. This hook allows us to
 * act on all major node operations, so we can manage our additional data
 * appropriately.
 */
function nodeapi_example_nodeapi(&$node, $op, $teaser, $page) {
  switch ($op) {
    // When the content editing form is submitted, we need to validate the input
    // to make sure the user made a selection, since we are requiring the rating
    // field. We have to check that the value has been set to avoid showing an
    // error message when a new blank form is presented. Calling form_set_error()
    // when the field is set but zero ensures not only that an error message is
    // presented, but also that the user must correct the error before being able
    // to submit the node.
    case 'validate':
      if (variable_get('nodeapi_example_'. $node->type, TRUE)) {
        if (isset($node->nodeapi_example_rating) && !$node->nodeapi_example_rating) {
          form_set_error('nodeapi_example_rating', t('You must rate this content.'));
        }
      }
      break;

    // Now we need to take care of loading one of the extended nodes from the
    // database. An array containing our extra field needs to be returned.
    case 'load':
      // we match against vid in order to keep up with the current revision
      $rating = db_result(db_query('SELECT rating FROM {nodeapi_example} WHERE vid = %d', $node->vid));
      return array('nodeapi_example_rating' => $rating);
      break;

    // Insert is called after the node has been validated and saved to the
    // database. It gives us a chance to create our own record in the database.
    case 'insert':
      if (variable_get('nodeapi_example_'. $node->type, 0)) {
        db_query('INSERT INTO {nodeapi_example} (nid, vid, rating) VALUES (%d, %d, %d)', $node->nid, $node->vid, $node->nodeapi_example_rating);
      }
      break;

    // Update is called when an existing node has been changed. Here, we use a
    // DELETE then an INSERT rather than an UPDATE. The reason is that a node
    // created before this module was installed won't already have a rating
    // saved so there would be nothing to update.
    case 'update':
      if (variable_get('nodeapi_example_'. $node->type, 0)) {
        db_query('DELETE FROM {nodeapi_example} WHERE vid = %d', $node->vid);
        db_query('INSERT INTO {nodeapi_example} (nid, vid, rating) VALUES (%d, %d, %d)', $node->nid, $node->vid, $node->nodeapi_example_rating);
      }
      break;

    // Delete is called when the node is being deleted, it gives us a chance
    // to delete the rating too.
    // This will delete all revisions as well.
    case 'delete':
      db_query('DELETE FROM {nodeapi_example} WHERE nid = %d', $node->nid);
      break;

    // When a node revision is deleted, we need to remove the corresponding
    // record from our table. The only way to handle revision deletion is by
    // implementing hook_nodeapi().
    case 'delete revision':
      // Notice that we're matching a single revision based on the node's vid.
      db_query('DELETE FROM {nodeapi_example} WHERE vid = %d', $node->vid);
      break;

    // Finally, we need to take care of displaying our rating when the node is
    // viewed. This operation is called after the node has already been prepared
    // into HTML and filtered as necessary, so we know we are dealing with an
    // HTML teaser and body. We will inject our additional information at the front
    // of the node copy.
    //
    // Using nodeapi('view') is more appropriate than using a filter here, because
    // filters transform user-supplied content, whereas we are extending it with
    // additional information.
    case 'view':
      if (variable_get('nodeapi_example_'. $node->type, 0)) {
        $node->content['nodeapi_example'] = array(
        '#value' => theme('nodeapi_example_rating', $node->nodeapi_example_rating),
        '#weight' => -1,
        );
      }
      break;
  }
}

/**
 * Implementation of hook_theme().
 *
 * This lets us tell Drupal about our theme functions and their arguments.
 */
function nodeapi_example_theme() {
  return array(
    'nodeapi_example_rating' => array(
      'arguments' => array('rating'),
    ),
  );
}

/**
 * A custom theme function.
 *
 * By using this function to format our rating, themes can override this presentation
 * if they wish; for example, they could provide a star graphic for the rating. We
 * also wrap the default presentation in a CSS class that is prefixed by the module
 * name. This way, style sheets can modify the output without requiring theme code.
 */
function theme_nodeapi_example_rating($rating) {
  $options = array(
    0 => t('Unrated'),
    1 => t('Poor'),
    2 => t('Needs improvement'),
    3 => t('Acceptable'),
    4 => t('Good'),
    5 => t('Excellent'));
  $output = '<div class="nodeapi_example_rating">';
  $output .= t('Rating: %rating', array('%rating' => $options[(int) $rating]));
  $output .= '</div>';
  return $output;
}

/**
 * @} End of "defgroup nodeapi_example".
 */